Genes in space and time

Genetic study of the Arunachal and bonnet macaques

Genetic study on the two primate species, one from the plains of Indian peninsula, the bonnet macaque and the other from the mountainous southern edge of the Tibetan plateau, the Arunachal macaque in order to understand their relatedness, distribution, population structure and demographic histories

The curious case of Arunachal macaque

We did a genetic analysis of four macaque species—the bonnet macaque, Assamese macaque, Tibetan macaque and the Arunachal macaque. Our genetic study shows that the Arunachal macaque is distinct from the Assamese, Tibetan and bonnet macaques. The Arunachal macaque resembles the Assamese and Tibetan macaques in its morphology (physical features) possibly because the three species occur in similar ecological conditions. However, it is genetically distant from them, perhaps because the River Brahmaputra acts as a barrier to the mixing and dispersal of their genes. Interestingly, however, the Arunachal macaque is genetically very close to its geographically-distant cousin, the bonnet macaque although they are morphologically very different.

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Population genetic structure and distribution

Based on genetic analyses, we compared factors that may influence the distribution pattern of populations of the Arunachal and bonnet macaques. The unique geographical location in the Tibetan Plateau, rugged topography, socio-behavioural characteristics and historic geological events has influenced the distribution of populations of Arunachal macaque. On the contrary, the bonnet macaque shows an extensive, continuous distribution of populations organised at a fine-scale.

What influences the demography history?

Arunachal macaque, an edge primate species have yielded a very complex image of how geographical features such as latitude and altitude, animal physiology and climate change in the past may have together influenced its population size historically. Populations, for instance, show a signature of expansion, right after the Last Glacial Maximum thousands of years ago. This study also underscores the possibility that a cold-tolerant species like the Arunachal macaque, which could withstand historical climate change and grow once the climate became conducive, could also be extremely vulnerable to anthropogenic exploitation, as is perhaps indicated by its more recent mid-Holocene population decline. The demographic history of the tropical bonnet macaque, however, indicates that the temperate glaciations may not have any effect on its population size; instead, the historical fluctuations in monsoon patterns in Indian subcontinent may have been an important factor that drove population size change in this species. Interestingly, we would have expected a generalist species like the bonnet macaque to be extremely adaptable to changes in its environment but found that a large-scale climate change could profoundly affect the species.

Human–macaque interactions constitute a complex phenomenon influencing perhaps the biology of the macaque more profoundly than ours. At the population level, humans tend to influence the distribution, demography, immunology and even behaviour of the macaque species they interact with though none of these interactions are ever simple. These works at different levels, interacting, in turn, with other environmental factors and most of these impacts are likely to have genetic consequences over the long term. In this chapter, we reviewed available literature on anthropogenic impacts on macaque populations. We should, however, stress that our current state of knowledge, unfortunately, suffers from a serious lack of insight into such genetic impacts. There is, therefore, a dire need for long-term genetic monitoring programmes to understand the effect of anthropogenic factors on the dispersal and demography of different macaque species.

Journal Article

2010

Genetic Polymorphism in the Serotonin Transporter Promoter Region and Ecological Success in Macaques

A well-characterised sequence length poly- morphism in the serotonin transporter promoter region (5-HTTLPR) influences individual behavioural traits and cognitive abilities in humans and rhesus macaques. Maca- ques have been classified into four continuous grades on the basis of their behavioural attributes, ranging from highly hierarchical and nepotistic species to the most egalitarian and tolerant ones. A comparative study of several species that spanned these grades revealed only rhesus macaques to be polymorphic at the 5-HTTLPR and concluded that the polymorphism was responsible for their despotic and aggressive behaviour (Wendland et al., Behav Genet 36:163–172, 2006). We studied wild populations of three other species and found that the egalitarian and tolerant bonnet and Arunachal macaques are also polymorphic while liontailed macaques, although belonging to the same group, are monomorphic. We thus reject a role for this particular polymorphism in interspecific behavioural vari- ability and show that polymorphic species enjoy greater ecological success possibly due to their higher infraspecific variability in individual behavioural traits.

Journal Article

2007

Phylogenetic relationships and morphometric affinities of the Arunachal macaque Macaca munzala, a newly described primate from Arunachal Pradesh, northeastern India

A new species of primate, the Arunachal macaque Macaca munzala, belonging to the sinica species-group of the genus, was described from northeastern India in 2005, and, based on its appearance and distribution, hypothesised to be closely related to M. assamensis and M. thibetana. We subsequently obtained an entire adult male specimen and tissue remains from two other M. munzala individuals. Molecular analyses establish the distinct identity of the species and indicate a time of origin of c. 0.48 mya for it. The species also shows close phylogenetic affinities with the allopatric M. radiata and with the geographically closer M. assamensis and M. thibetana, possibly mediated by male introgression from an ancestral M. assamensis–M. thibetana stock into an ancestral M. munzala stock. Morphometric analyses, on the other hand, reiterate its close similarity only with M. assamensis and M. thibetana, presumably resulting from convergent evolution under similar ecological conditions and along a latitudinal gradient, as predicted by Bergmann’s and Allen’s rules.

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